The present invention relates to a water-bottom rubbles leveling apparatus for leveling the upper surface of a rubble-mound or riprap formed by rubbles pilled up on the bottom of the water.
Many of outer facilities in harbors such as breakwaters and revetments are caisson type composite dikes formed by sinking a concrete caisson onto a rubble-mound which comprises a pile of rubbles on the bottom of the water. Generally, such caisson type composite dikes are constructed through the following stage of works: (1) sinking rubbles onto the bottom of the water from a ship, (2) leveling the rubbles, (3) installing a caisson from a ship, (4a) packing the caisson with sand, (4b) installing blocks, and (5) completing the top of the caisson.
The work for leveling the upper surface of the above-mentioned rubble-mound indicated at the reference numeral 1 has heretofore been conducted manually by divers.
Although most of the other construction works in harbors have already been mechanized, the foregoing rubble leveling work still relies on the divers' manual work. But the efficiency of the rubble leveling work by divers is extremely poor, and there is an increasing demand for mechanization under the background as will be described below.
(1) Most of the divers are of advanced ages because the number of persons who wish to become a diver is small, showing a tendency to shortage. (2) The number of large-scale construction works which require a rapid execution of work is increasing. (3) Harbors tend to extend to the offing, thus resulting in increased depth of water. (4) From the aspect of safety supervision, it is necessary to avoid human heavy labor involving some risks.
In view of the circumstances mentioned above, some methods for a mechanized execution of works have so far been proposed and tried, but have not been practically adopted yet because those methods involve problems in point of leveling accuracy, working efficiency, the size of stones capable of being leveled and cost.
Usually, crushed stones used as rubbles are each 30 to 200 kg in weight and 30 to 60 cm in size, and when sunk onto the water bottom, those stones form unevenness corresponding to .+-.50 cm or more. For a stable installation of caisson, it is required to level such unevenness with a very high accuracy, for example, within .+-.5 cm.